This invention relates to the interaction of computer applications across a heterogeneous data processing network. Specifically, this invention relates to the organization of a data processing network in accordance with an object-oriented model and the interaction of independent applications across such a heterogeneous network environment.
Computers communicate with each other over data processing networks. The computers themselves are referred to generally as "nodes," and a specific type of computer, that is a specific type of hardware using a specific type of operating system, is referred to as a "platform." Networks containing different types of platforms are called "heterogeneous networks." One purpose for connecting platforms in a network is to provide different environments in which to execute application programs (referred to as "applications" for brevity) on shared data.
In the typical data processing network, different platforms and applications running on different platforms store information in their own specific manner. For example, in a VAX.VMS platform, text editing tasks may be accomplished using a TPU text editor, while in a MIPS.ULTRIX platform, text editing tasks may be accomplished using an EMACS text editor. Users of a network having both platforms may wish to use operations from the different text editors on the different platforms without having to know the details of those platforms and text editors.
This compatibility has not previously been possible. Instead, conventional networks require users of a heterogeneous network to employ the specific interface each application requires for operations on specific platforms. Conventional networks fail to provide users with a capability to communicate between applications using a standard interface.
As an example of the difficulties of interapplication communication on a conventional heterogeneous network, suppose that the user of a text editor application on one platform desired to access a multi-user data base retrieval service, such as DIALOG for scientific articles or LEXIS for court opinions, on another platform. To do so on a conventional network, the text editor application's operation would have to be suspended, and the data base retrieval service would have to be invoked using commands and messages specific to the data base retrieval service. The user would not only need to know the specific names of each service desired, but would also have to know the location of the service in the network and would have to be familiar with the different commands and command formats employed by each service.
As yet no standard interface has been developed to allow an application in one platform to invoke an application on a different platform in a heterogeneous network in an efficient and uncomplicated manner. Instead, conventional interapplication communication merely provides mechanisms for physically transporting messages and data between applications.
One example of a mechanism which is presently used to allow an application on one platform to communicate with an application on a different platform is a Remote Procedure Call (RPC) system. An RPC system on one platform responds to queries from an "invoking" application by first translating that application's messages into a network data format, and then transmitting the translated queries over the network to a receiving platform. At the receiving platform, another component of the RPC system decodes translated messages into queries in a data format acceptable to the application invoked. The original messages from the invoking platform, however, need to be consistent with a syntax dictated by the invoked application.
Another difficulty with conventional networks occurs when the application on a remote node is not currently loaded and running. Many RPC systems only allow remote invocation of applications that are already loaded and running. If this is not the case, the user of the client applications must find some way to load the server application on the remote platform before invoking it. This can be severely limiting.
One obstacle to implementing a network-wide system to facilitate interapplication communication has been the large amount of system resources which had been thought to be required of a system in order to handle all the different types of data, operations and applications in a network. As a network expands, the systems, resources, and requirements would increase as well, making many proposed implementations completely unwieldy.
There is, therefore, a need for an efficient and simple manner for applications on different platforms to be invoked, such as through a uniform and consistent interface. There is also a need for a dynamic invocation environment for applications in a distributed heterogeneous environment. This includes providing the ability to for applications that are not yet loaded and running to be invoked as well of those which are.